M-Tronic; Calibrating The Control Unit; Resetting The Control Unit To Factory Defaults; Testing - Stihl FS 240 Service Manual

7.

M-Tronic

The fully electronic M-Tronic engine
management system controls the
ignition timing and fuel flow, taking
all external conditions into account.
A basic or standard setting of the
carburetor is no longer required.
The M-Tronic electronically adjusts
the fuel-air mixture in the carburetor.
The M-Tronic controls all operating
states such as start, idle, part
throttle and full throttle while
accounting for the external
conditions, e.g., use at varying
attitudes, as well as changing
temperatures or fuel quality – the
carburetor does not have any
adjusting screws.
Troubleshooting and test
procedures are described in the
following chapters, Testing, b 7.3,
Troubleshooting, b 7.5.
7.1 Calibrating the control
unit
Calibration of the control unit may
be necessary if the outstanding
running behavior and usual
performance of the engine can no
longer be attained.
Sequence of operations for
calibration:
– Remove cutting attachment, all
mounting hardware for the
cutting attachment and the thrust
plate
58
– Let the engine warm up for
approx. 120 seconds at full
throttle; during this time, carry out
several short load changes (let
engine idle – then accelerate
again to full throttle)
– Let the engine idle for approx. 5
seconds
– Let the machine run four or five
times for approx. 30 seconds at
full throttle in the cut-off range.
Let the engine idle for periods of
approx. 5 seconds each between
the full-throttle phases.
7.2 Resetting the control unit
to factory defaults
If the control unit and/or the
carburetor is replaced in customer
service, the M-Tronic must be reset
to the factory defaults.
– Set choke lever to position }
– Start engine – do not blip the
throttle trigger!
– Let engine run in this start
position for at least 90 seconds
– Actuate the stop switch –
calibration is completed
The control unit is adjusted to the
carburetor while the engine runs in
the position Start}. The control
unit saves the information when the
engine is switched off immediately.
FS 240 C, FS 260 C, FS 360 C, FS 410 C, FS 460 C-M
7.3

Testing

7.3.1

Test preparations

The following steps must be carried
out before testing.
– Carry out troubleshooting
according to troubleshooting
chart, b 7.5
– Remove shroud, b 5.4
– Remove coarse dirt from around
the screwed connections, control
unit, switchgear, solenoid valve
and diagnostic jack
– Remove the air filter cover,
b 11.1
7.3.2

Connect the test lead

1
: Remove the plug (1)
: Connect M-Tronic test lead (1)
5910 840 0903 to the diagnostic
jack (arrow)
1